Regular testing of a fire system is required as per NFPA72. As a part of testing a fire system, it is important to validate that the audible/visible notification appliances on the Notification Appliance Circuit (NAC) are functioning properly. However, unlike the testing of the sensors, the testing of the NAC circuit can present some unique challenges. The sensors can be tested with little disturbance to the building occupants.
Devices on a NAC circuit, on the other hand, are designed to alert individuals to a fire and therefore, are meant to cause a disturbance. Depending on the building and its occupants, this can create challenges for both the occupants as well as those doing the testing. Sometimes, testing needs to be done late at night when the building is unoccupied. Often times, those doing the testing will activate the NAC circuit and literally run through the building to validate that all units are operating. This can also be challenging to ensure that each device is sounding since the overall noise is quite loud.
There are other times when a building is always occupied, such as a factory where three shifts result in the building being occupied for 24 hours per day. In that situation, employees may have to step outside while the testing is conducted. This results in lost production for the company. Even greater challenges arise with buildings that are always occupied, such as a hospital. In this case, patients cannot be easily moved outside. They either have to put up with the noise, or, more likely, the testing is simply not done.
One system for driving and controlling such devices is disclosed in U.S. Pat. No. 5,598,139 entitled “Fire Detecting System With Synchronized Strobe Lights”, which issued Jan. 28, 1997. The '139 patent is assigned to the assignee hereof and incorporated herein by reference.